1. Field of the Invention
The present invention relates generally to medical devices and more particularly to an improved trocar system having a mechanism for producing an audible signal when the trocar penetrates into an insufflated (pressurized) body cavity.
Least invasive surgical (LIS) techniques, such as laparoscopic, endoscopic, and arthroscopic surgery, are generally performed through small incisions using specialized instruments to perform desired surgical procedures. Usually, the instruments are introduced through a tube, such as a trocar cannula, while the physician observes manipulation of instruments through specialized imaging equipment, such as laparoscopes, endoscopes, arthroscopes, and the like. Such LIS techniques offer significant advantages over convention "open" surgical procedures. In particular, the LIS techniques are usually less traumatic, require a shorter recovery time, and are less costly than the corresponding conventional surgical technique.
Of particular interest to the present invention, laparoscopic surgery is generally performed within the abdominal cavity, with the abdominal wall raised by pressurization of the abdominal cavity (referred to as "insufflation" to create an open space for positioning of the laparoscope and manipulation of the surgical tools to perform the desired procedure. Insufflation is achieved by introducing an insufflation gas, typically carbon dioxide, through a Veress needle or other conduit which is introduced through the abdominal wall. One or more additional trocar cannulas are then introduced through the abdominal wall into the insufflated region between the abdominal wall and underlying organs created. Such trocar cannulas are typically introduced in combination with an obturator, which is a rigid shaft removably received within a central lumen of the trocar cannula and having a sharpened tip which extends out of the distal end of the cannula. In this way, the trocar cannula and obturator can together be penetrated through the abdominal wall relying on the sharpened distal end of the obturator. The obturator can then be removed, leaving the lumen of the trocar cannula available for access to the abdominal cavity.
While generally successful, the sharpened distal tip of the obturator presents a risk of injury to underlying body structures when the combined trocar cannula and obturator is introduced through the abdominal wall. In order to avoid such injury, it is important that the sharpened distal tip of the obturator be stopped or somehow protected immediately after the tip penetrates through posterior surface of the abdominal wall.
One such approach for protecting the tip relies on a spring-loaded shield mounted concentrically over the obturator. The shield is drawn proximally by contact with tissue as the obturator and trocar cannula are advanced through the abdominal wall. As soon as the obturator enters the abdominal cavity, however, the shield springs back over the sharpened tip of the obturator to protect underlying body organs from damage. Such an approach has been generally successful, but suffers from certain drawbacks. In particular, in some cases the shield may become jammed or may simply not respond quickly enough to cover the obturator before contact with body structures in the abdominal cavity occurs.
Even when responding as intended, the sharpened obturator tip is still able to penetrate beyond the tissue by a short distance, approximately 1 cm to 3 cm, before the shield redeploys over the entire length of the obturator. Thus, there remains a risk of injury during this length of unprotected travel. An alternative approach for protecting the obturator tip relies on a spring-loaded core within the obturator, where the core retracts as the obturator is advanced. Although an improvement over the external shield, the core can still become jammed.
For these reasons, it would be desirable to provide alternative apparatus and methods for protecting a patient during introduction of a trocar cannula and obturator system during surgical procedures, particularly laparoscopic procedures. It would be further desirable to provide protection which is responsive immediately as the sharpened distal tip of an obturator enters an insufflated abdominal cavity. Such apparatus and methods should be reliable, easy to implement, compatible with a wide variety of trocar cannula and obturator systems, and be relatively inexpensive to produce.
2. Description of the Background Art
Trocar cannula and obturator systems are known. See, e.g., U.S. Pat. Nos. 5,122,122; 5,127,909; 5,053,016; and 4,943,280. A drainage catheter which is introduced using a trocar and which includes a pressure-responsive silicone elastomer "signal dome" is disclosed in U.S. Pat. No. 4,944,724. Needles and syringes having pressure indicating devices are described in U.S. Pat. Nos. 4,801,293; 4,710,172; and 4,623,335. A Veress needle having a pressure gauge is disclosed in U.S. Pat. No. 3,982,533. Other patents relevant to the state-of-the-art include U.S. Pat. Nos. 4,404,924; 2,976,865; and 2,646,042. Karl Storz GmbH sells a trocar cannula and obturator system, where the obturator includes a pressure release vent which opens to a port immediately proximal to a sharpened distal tip.